// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2012 Désiré Nuentsa-Wakam <desire.nuentsa_wakam@inria.fr>
// Copyright (C) 2012 Gael Guennebaud <gael.guennebaud@inria.fr>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

/* 
 
 * NOTE: This file is the modified version of [s,d,c,z]panel_bmod.c file in SuperLU 
 
 * -- SuperLU routine (version 3.0) --
 * Univ. of California Berkeley, Xerox Palo Alto Research Center,
 * and Lawrence Berkeley National Lab.
 * October 15, 2003
 *
 * Copyright (c) 1994 by Xerox Corporation.  All rights reserved.
 *
 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY
 * EXPRESSED OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
 *
 * Permission is hereby granted to use or copy this program for any
 * purpose, provided the above notices are retained on all copies.
 * Permission to modify the code and to distribute modified code is
 * granted, provided the above notices are retained, and a notice that
 * the code was modified is included with the above copyright notice.
 */
#ifndef SPARSELU_PANEL_BMOD_H
#define SPARSELU_PANEL_BMOD_H

namespace Eigen {
namespace internal {

    /**
 * \brief Performs numeric block updates (sup-panel) in topological order.
 * 
 * Before entering this routine, the original nonzeros in the panel
 * were already copied into the spa[m,w]
 * 
 * \param m number of rows in the matrix
 * \param w Panel size
 * \param jcol Starting  column of the panel
 * \param nseg Number of segments in the U part
 * \param dense Store the full representation of the panel 
 * \param tempv working array 
 * \param segrep segment representative... first row in the segment
 * \param repfnz First nonzero rows
 * \param glu Global LU data. 
 * 
 * 
 */
    template <typename Scalar, typename StorageIndex>
    void SparseLUImpl<Scalar, StorageIndex>::panel_bmod(const Index m,
                                                        const Index w,
                                                        const Index jcol,
                                                        const Index nseg,
                                                        ScalarVector& dense,
                                                        ScalarVector& tempv,
                                                        IndexVector& segrep,
                                                        IndexVector& repfnz,
                                                        GlobalLU_t& glu)
    {
        Index ksub, jj, nextl_col;
        Index fsupc, nsupc, nsupr, nrow;
        Index krep, kfnz;
        Index lptr;   // points to the row subscripts of a supernode
        Index luptr;  // ...
        Index segsize, no_zeros;
        // For each nonz supernode segment of U[*,j] in topological order
        Index k = nseg - 1;
        const Index PacketSize = internal::packet_traits<Scalar>::size;

        for (ksub = 0; ksub < nseg; ksub++)
        {  // For each updating supernode
            /* krep = representative of current k-th supernode
     * fsupc =  first supernodal column
     * nsupc = number of columns in a supernode
     * nsupr = number of rows in a supernode
     */
            krep = segrep(k);
            k--;
            fsupc = glu.xsup(glu.supno(krep));
            nsupc = krep - fsupc + 1;
            nsupr = glu.xlsub(fsupc + 1) - glu.xlsub(fsupc);
            nrow = nsupr - nsupc;
            lptr = glu.xlsub(fsupc);

            // loop over the panel columns to detect the actual number of columns and rows
            Index u_rows = 0;
            Index u_cols = 0;
            for (jj = jcol; jj < jcol + w; jj++)
            {
                nextl_col = (jj - jcol) * m;
                VectorBlock<IndexVector> repfnz_col(repfnz, nextl_col, m);  // First nonzero column index for each row

                kfnz = repfnz_col(krep);
                if (kfnz == emptyIdxLU)
                    continue;  // skip any zero segment

                segsize = krep - kfnz + 1;
                u_cols++;
                u_rows = (std::max)(segsize, u_rows);
            }

            if (nsupc >= 2)
            {
                Index ldu = internal::first_multiple<Index>(u_rows, PacketSize);
                Map<ScalarMatrix, Aligned, OuterStride<>> U(tempv.data(), u_rows, u_cols, OuterStride<>(ldu));

                // gather U
                Index u_col = 0;
                for (jj = jcol; jj < jcol + w; jj++)
                {
                    nextl_col = (jj - jcol) * m;
                    VectorBlock<IndexVector> repfnz_col(repfnz, nextl_col, m);  // First nonzero column index for each row
                    VectorBlock<ScalarVector> dense_col(dense, nextl_col, m);   // Scatter/gather entire matrix column from/to here

                    kfnz = repfnz_col(krep);
                    if (kfnz == emptyIdxLU)
                        continue;  // skip any zero segment

                    segsize = krep - kfnz + 1;
                    luptr = glu.xlusup(fsupc);
                    no_zeros = kfnz - fsupc;

                    Index isub = lptr + no_zeros;
                    Index off = u_rows - segsize;
                    for (Index i = 0; i < off; i++) U(i, u_col) = 0;
                    for (Index i = 0; i < segsize; i++)
                    {
                        Index irow = glu.lsub(isub);
                        U(i + off, u_col) = dense_col(irow);
                        ++isub;
                    }
                    u_col++;
                }
                // solve U = A^-1 U
                luptr = glu.xlusup(fsupc);
                Index lda = glu.xlusup(fsupc + 1) - glu.xlusup(fsupc);
                no_zeros = (krep - u_rows + 1) - fsupc;
                luptr += lda * no_zeros + no_zeros;
                MappedMatrixBlock A(glu.lusup.data() + luptr, u_rows, u_rows, OuterStride<>(lda));
                U = A.template triangularView<UnitLower>().solve(U);

                // update
                luptr += u_rows;
                MappedMatrixBlock B(glu.lusup.data() + luptr, nrow, u_rows, OuterStride<>(lda));
                eigen_assert(tempv.size() > w * ldu + nrow * w + 1);

                Index ldl = internal::first_multiple<Index>(nrow, PacketSize);
                Index offset = (PacketSize - internal::first_default_aligned(B.data(), PacketSize)) % PacketSize;
                MappedMatrixBlock L(tempv.data() + w * ldu + offset, nrow, u_cols, OuterStride<>(ldl));

                L.setZero();
                internal::sparselu_gemm<Scalar>(L.rows(), L.cols(), B.cols(), B.data(), B.outerStride(), U.data(), U.outerStride(), L.data(), L.outerStride());

                // scatter U and L
                u_col = 0;
                for (jj = jcol; jj < jcol + w; jj++)
                {
                    nextl_col = (jj - jcol) * m;
                    VectorBlock<IndexVector> repfnz_col(repfnz, nextl_col, m);  // First nonzero column index for each row
                    VectorBlock<ScalarVector> dense_col(dense, nextl_col, m);   // Scatter/gather entire matrix column from/to here

                    kfnz = repfnz_col(krep);
                    if (kfnz == emptyIdxLU)
                        continue;  // skip any zero segment

                    segsize = krep - kfnz + 1;
                    no_zeros = kfnz - fsupc;
                    Index isub = lptr + no_zeros;

                    Index off = u_rows - segsize;
                    for (Index i = 0; i < segsize; i++)
                    {
                        Index irow = glu.lsub(isub++);
                        dense_col(irow) = U.coeff(i + off, u_col);
                        U.coeffRef(i + off, u_col) = 0;
                    }

                    // Scatter l into SPA dense[]
                    for (Index i = 0; i < nrow; i++)
                    {
                        Index irow = glu.lsub(isub++);
                        dense_col(irow) -= L.coeff(i, u_col);
                        L.coeffRef(i, u_col) = 0;
                    }
                    u_col++;
                }
            }
            else  // level 2 only
            {
                // Sequence through each column in the panel
                for (jj = jcol; jj < jcol + w; jj++)
                {
                    nextl_col = (jj - jcol) * m;
                    VectorBlock<IndexVector> repfnz_col(repfnz, nextl_col, m);  // First nonzero column index for each row
                    VectorBlock<ScalarVector> dense_col(dense, nextl_col, m);   // Scatter/gather entire matrix column from/to here

                    kfnz = repfnz_col(krep);
                    if (kfnz == emptyIdxLU)
                        continue;  // skip any zero segment

                    segsize = krep - kfnz + 1;
                    luptr = glu.xlusup(fsupc);

                    Index lda = glu.xlusup(fsupc + 1) - glu.xlusup(fsupc);  // nsupr

                    // Perform a trianglar solve and block update,
                    // then scatter the result of sup-col update to dense[]
                    no_zeros = kfnz - fsupc;
                    if (segsize == 1)
                        LU_kernel_bmod<1>::run(segsize, dense_col, tempv, glu.lusup, luptr, lda, nrow, glu.lsub, lptr, no_zeros);
                    else if (segsize == 2)
                        LU_kernel_bmod<2>::run(segsize, dense_col, tempv, glu.lusup, luptr, lda, nrow, glu.lsub, lptr, no_zeros);
                    else if (segsize == 3)
                        LU_kernel_bmod<3>::run(segsize, dense_col, tempv, glu.lusup, luptr, lda, nrow, glu.lsub, lptr, no_zeros);
                    else
                        LU_kernel_bmod<Dynamic>::run(segsize, dense_col, tempv, glu.lusup, luptr, lda, nrow, glu.lsub, lptr, no_zeros);
                }  // End for each column in the panel
            }

        }  // End for each updating supernode
    }      // end panel bmod

}  // end namespace internal

}  // end namespace Eigen

#endif  // SPARSELU_PANEL_BMOD_H
